Egoism can be a descriptive or a normative position. Psychological egoism, the most famous descriptive position, claims that each person has but one ultimate aim: her own welfare. Normative forms of egoism make claims about what one ought to do, rather than describe what one does do. Ethical egoism claims that it is necessary and sufficient for an action to be morally right that it maximize one's self-interest. Rational egoism claims that it is necessary and sufficient for an action to be rational that it maximize one's self-interest.